The present invention is directed to a strapping machine feed system. More particularly, the present invention is directed to a strapping machine feed system in which strap is refed following a strap error or fault.
Strapping machines are well known in the art for securing straps around loads. One type of known strapper is a stationary unit that includes a strapping head or weld head and drive mechanism mounted within a frame. A chute is mounted to the frame, through which the strapping material is fed. In a typical arrangement, a table-top or work surface is likewise mounted to the frame.
In a typical stationary strapper, the chute is mounted from about the work surface, and the strapping head is mounted below the work surface. Strap is fed from a source or dispenser to the strapping or weld head. The strapping head provides a number of functions. First, it includes a plurality of grippers for gripping portions of the strap during the course of a strapping operation. The strapping head also includes a cutter to cut the strap from a strap source or supply. Last, the strapping head includes a sealer to seal an overlying course of strapping material onto itself. This seal is commonly referred to as a weld and is effected by heating overlying courses of the strap by use of a vibrating element or a heated element.
Strapping material is fed from the dispenser into the strapping head first via a pair of infeed wheels and second via a feed assembly. The infeed wheels are typically located immediately inside of the strapping machine (e.g., inside of an enclosure or cabinet). The infeed wheels facilitate smoothly feeding the strapping material into the strapper and supplying strapping material into the slack box. The slack box is an area between the infeed wheels and the strapping head that is used to store a length of “slack” strapping material for use by the strapping head and is also an area for storing take-up strap that has been rewound or tensioned around the load.
The feed assembly includes a pair of tensioning wheels and a pair of feed wheels. The tensioning wheels are locate downstream of the infeed wheels, and a guide extends between the tensioning and feed wheels. The slack box is disposed about the guide area, between the infeed and tensioning wheels.
The feed wheels are located between the tensioning wheels and the strapping head. The feed wheels feed the strap material into the strapping head (and around the strap chute). A guide is disposed between the tensioning wheels and the feed wheels to provide a pathway for the strap as it is fed into the strapping head by the feed wheels and as it is pulled from the strapping head (and from around the chute) by the tensioning wheels.
In the event a strap error occurs, as by a failure of the gripper to grip the leading end of the strap, during the tensioning cycle, the strap will be over-retracted or over-pulled by the tensioning wheels. When this occurs, the strap is pulled rearwardly to the extent that is has essentially pulled out of the strap path. Pulling the strap from the path results in a machine fault. Operator attention is then required to stop machine operation and refeed strap into the feed system to resume operation.
Accordingly, there is a need for a strapping machine having a strap feeding and tensioning system with automatic refeed. Desirably, such a system automatically detects a strap error or fault, stops strap retraction or take-up and refeeds the strap into the strapping head following that error or fault. More desirably, such a system refeeds the strap into the strapping head without additional parts or assemblies beyond those employed for feeding and tensioning the strap material during normal machine operations.